Scuba diving is a unique and enjoyable recreational experience. It is estimated that, every day, over 75,000 persons participate in the sport at thousands of diving resorts and operations worldwide.
Operationally, one aspect of the uniqueness of diving is that underwater communication is extremely limited and communication between divers and the surface is almost non-existent. The diving industry has developed several techniques to facilitate underwater communication—hand signals, writing on a slate, tapping on one's tank, and electronic communication devices. The first three require a close proximity for the communicating divers and, in the case of electronic means, are prohibitively expensive for all but commercial divers.
Limited visibility exacerbates communication difficulty. The “best” recreational ocean diving sites around the world have 150 feet of underwater visibility with a few locations having occasional periods of 200 feet. Most, however, have 60 feet or less. With few exceptions, visibility at inland sites drops below 20 feet. Considering that ocean currents in many dive areas may have a velocity of one to two knots, a diver in perfect visibility conditions can drift out of sight in less than 60 seconds.
Visibility is further reduced by underwater topography which may include coral or rock formations. Lastly, diving operators at most recreational dive sites offer a “night-diving”experience. Obviously, this limits communication even further and complicates the divemaster's supervisory responsibilities.
Major scuba-diving-certifying organizations have attempted to mitigate these risks by establishing smart and, fortunately, well-accepted rules: always dive with and stay close to a “buddy”; evaluate conditions carefully and seek orientation with a local dive shop before diving; plan the dive carefully, follow the plan once underwater, surface when one becomes separated from the group; etc. The fact remains, though, that the communication options available to the average recreational diver when in distress or when separated from the group are extremely limited. In contrast with a comparable land-based activity, backpacking, a lone hiker has the option of carrying an emergency satellite beacon should he become injured or miss-oriented. Divers have no such long-range option. At best, some recreational divers carry only a simple whistle or inflatable tube for use at the surface.